Geothermal Power: The renewable alternative that can’t be ‘microwaved

Whenever power outage strongly hits the country, the conversations regarding the robustness of the electricity industry resurfaces, and the recent weeks-long nationwide power rationing was no exception.

Hydropower makes up 37 percent of Tanzania’s electricity generation, the second largest after natural gas, according to Power System Master Plan-2020. The generation is water-intensive and dependent, making it extremely vulnerable to droughts due to climate change.

Recently, there was a significant dwindling of water levels in the Kihansi, Kidatu and Pangani hydropower dams making it infeasible to spin the power turbines.

The declining levels meant a loss of 345 Megawatts in the national grid, forcing the power utility, Tanesco, to shed load with rolling daily blackouts. It is clear that when water resources supply gets interrupted, hydropower cannot fight back.

The ‘dumsor’ sparked a furore on social and traditional media, primarily centred on the incessant over-reliance of hydropower generation despite its outlook being less promising. Solar, wind and geothermal power technologies topped the list of generational alternatives that many proposed to speedily and reliably put the electricity supply and demand configuration in a continuous physical equilibrium. How realistic? Let’s make an analysis.

Despite their inherent intermittences, wind and solar power can be rapidly installed upon the confirmation of the optimistic outcomes of on-surface resources appraisals. On the contrary, geothermal power is distinctly characterised by high availability and independence from weather conditions - a suitable complement to hydropower. The geothermal surface surveys, on the other hand, are primarily geared towards siting the most promising targets of exploration wells. These surveys, no matter how rigorous or positive they can be, don’t guarantee the existence of the commercial geothermal resource – there are no geothermists with eyes beneath the earth’s surface.

Developing geothermal power, therefore, requires one more decisive, risky, costly and lengthy timeline barrier ahead – the subsurface resource assessment.

That is to say, the accessibility, characteristics, magnitude, productivity and utilisation opportunities of the geothermal resource hinge on the outcomes of exploratory drilling. This explains why the commercial viability and overall bankability of the geothermal power projects can only be established when wells are successfully drilled and tested. Simply put, in the absence of geothermal wells–considered as the veins and arteries of any geothermal development, there is no geothermal power.

A useful rule of thumb is that at least three large and deep exploration wells are drilled as the first step in the field confirmation stage. The global success ratios for these wells are estimated at 50-59 percent, reported the International Finance Corporation.

This phase alone attracts an up-front investment in the magnitude of up to Sh50 billion, according to the mid-range estimates of the World Bank ESMAP handbook.

The recent International Renewable Energy Agency guideline estimated the figures of such an endeavour to be in the range of Sh60–80 billion. This significant up-front proportion of the public funds is obviously lost if no resource is found.

The timeline needed to put geothermal power plants online varies considerably between projects in various countries. The WB guidelines put seven years span for the 50 Megawatts of geothermal power plant – which, I’ll argue in a moment being wildly optimistic. The Olkaria-I (45MW, the first geothermal power plant in Kenya) was commissioned in 1981. But, the surface and subsurface explorations took three decades.

The Menengai geothermal fields- Kenya with a planned capacity of 105MW started exploration in 2011, and yet to put a Megawatt on the grid. There are lots of valid reasons for these trends ranging from the inherent up-front resource risks, financing obstacles to unfavourable policy instruments.

The Power System Master Plan- 2020 forecasted the commission of the first 30MW of geothermal power plant by 2023 from the Ngozi Field, thereafter the 60MW from Kiejo-Mbaka Field by the year 2024. The Master Plan time-phased budgets for Ngozi and Kiejo-Mbaka are $75.7 million and $151.3 million respectively--to be government-financed between 2021 and 2024. With the complexity and dynamics of subsurface characteristics, government budgetary constraints, one cannot simply put a definite number to how quick these geothermal plants will come online – their development cannot simply be microwaved.

With the above reality in mind, it should come as no surprise to you that these plants will never come online as projected. Without being political, the greenfield geothermal power development takes time compared to those of solar and wind power for reasons expounded. Industry innovations, competent institutions, flexible business models and policy support mechanisms are the key instruments to shorten the geothermal longer lead times to probably less than a decade, and subsequently, allow the industry to live up to its significant promise.

Chagaka Kalimbia is an energy specialist. He currently works as a principal research and innovation engineer with the Tanzania Geothermal Development Company, a subsidiary of Tanesco. He can be reached through [email protected]